Digital imaging systems have experienced vast improvements in recent years. For example, improvements in memory capacity and microprocessor speeds have resulted in significant improvements for digital imaging systems including increased processing speeds and increased available storage. These improvements have led to increased popularity and acceptance of digital cameras by commercial entities as well as individuals.
Digital imaging systems including digital cameras have enjoyed significant improvements in resolution and are capable of producing high-quality photographs. The ability to display images in real time without having to wait for the development of exposures as required in analog systems is a significant improvement over conventional analog devices. Additional advantages of digital cameras enable an individual to download digital files of images from the digital camera to an associated host computer and/or printer. This downloading enables images to be communicated to remote locations using the Internet or other network system. Digital information of images may also be conveniently stored using flash memory, floppy disk, optical disk, or other storage device configurations.
Digital cameras may utilize a color filter array (CFA) of sensors which form data of a subject image and a plurality of mosaics individually including information regarding one color. Subsequently, the mosaic images undergo a demosaicing process wherein information for more than one color is provided at individual pixel locations. Some arrangements utilize interpolation in demosaicing operations to populate additional color information at respective pixel locations.
Denoising and sharpening may be simultaneously performed in conjunction with a demosaicing processing operation. However, denoising and sharpening capabilities may be limited by essentially linear, non-adaptive, and translation invariant demosaicing operations. These limitations are evident by relatively weak denoising strength and oversharpening of artifacts near strong edges. A relatively high amount of sharpening is likely to oversharpen strong transitions within images, in particular, transitions between dark and bright regions. Further, a relatively high amount of denoising is likely to over-smooth an output image causing it to look blurred.
Adaptive filtering may be utilized wherein different filtering kernels are utilized depending upon leading edge directions to solve the aforementioned problems. The output quality of these operations is limited by the number of different possible directions used in a classifier. Additionally, artifacts near high-curvature edges, such as corners and some kinds of texture, may result. It is desired to provide improved methods and apparatus for processing digital image data.